1. Field of the Invention
The present invention relates generally to a slide bead coating method and apparatus, and more particularly to a slide bead coating method and apparatus for coating a liquid coating composition on a flexible support (hereinafter referred to as "a web") in order to manufacture photographic film, photographic print paper, a magnetic recording tape, an adhesive tape, pressure sensitive paper, an offset plate, a sheet battery, etc.
2. Description of Related Art
A slide bead coating method has been proposed to apply the coating solution on the surface of the continuously-traveling web.
U.S. Pat. No. 2,761,791 teaches a multiple layer slide bead coating apparatus. In this apparatus, multiple coating solutions, which flow down a slide surface of a coating hopper, form a bead at a position where the coating solutions meet the continuously-traveling web at the front end of the slide surface. The coating solutions are applied on the surface of the web by the bead. Thus, it is important for the above-mentioned coating apparatus to form a stable bead.
The above-mentioned coating apparatus must accommodate webs which have a variety of widths, and the width of the coating solutions flowing down the slide surface must be adjusted according to the width of the web.
In an example of the method for adjusting the width of the coating solution, a guide plate is used which is disclosed in Japanese Patent Provisional Publication No. 57-110364. In this method, a pair of guide plates are provided from the rear end to the front end of the slide surface at both side edges in the direction of the width of the slide surface in order to adjust the width of the coating solution.
In the conventional slide bead coating apparatus using the guide plates, however, the bead formation is unstable at both side edges in the direction of the width of the coating solutions. For this reason, the coating solutions may not be coated on the edge region of the web. Since the edge region must be cut and removed in the after process, an additional step of cutting the edge region must be executed and the yield is lowered.
The coating sequence must be stopped to adjust a distance between the guide plates every time the width of the web changes. Thus, the working efficiency is sometimes lowered drastically due to a loss of time resulting from the stopping of the operation.